AMBER Archive (2006)

Subject: Re: AMBER: vlimit exceeded

From: David A. Case (case_at_scripps.edu)
Date: Thu May 18 2006 - 07:24:49 CDT


On Thu, May 18, 2006, aixiaoli wrote:
>
> Equilibration.in
> equilibration structure
> &cntrl
> imin=0,
> ntc=1,ntwx=1000,
> cut=15.0,igb=1,saltcon=0.2,gbsa=1,
> ntpr=1000,
> nstlim=20000,dt=0.001,
> ntt=3,gamma_ln = 1.0,tempi=100.0,temp0=300.0,
> ntx=1,irest=0,ntb=0,
> nscm=1000,
> &end
>
> vlimit exceeded for step 1079; vmax = 469.6312
> vlimit exceeded for step 1082; vmax = 24.5541
> vlimit exceeded for step 1083; vmax = 21.9756
> vlimit exceeded for step 1084; vmax = 21.4498
> vlimit exceeded for step 1089; vmax = 20.2899
> vlimit exceeded for step 1091; vmax = 21.6526
> vlimit exceeded for step 1092; vmax = 20.3968

I don't see anything wrong with your input. If you don't get more of these
messages (e.g. every step), it was probably due to some quirk in the starting
coordinates. If you think your starting structure is a good one, it is most
common to equilibrate with restraints on the coordinates (i.e. with ntr=1).
Once the system is equilibrated at 300K, you can remove the constraints, yet
be sure that your structure is still pretty close to the starting one.

A handful of vlimit errors is not necessarily something to worry about, but
you should certainly check that your structure is still in good shape.

....dac

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